Page:Walker (1888) The Severn Tunnel.djvu/43

8 present village of Caerwent, once the famous Roman station, ‘Venta Silurum.’ The Roman walls remain in fair preservation, and it is believed, that when this station was held by the Roman Legions, the tide from the Severn flowed up to the base of the southern wall, and that the rings to which the boats were moored still remain.

Where these tides flowed is now a rough piece of marsh-land, through which the little river Neddern passes to join the Severn.

The whole of the ground in the marsh is rotten, and before the tunnel was commenced there were enormous springs of bright, clear water rising up in several places.

At about 2 miles farther north than Caerwent, the hills of Wentwood are met with, with ‘Grey Hill’ standing in the foreground. The first spurs of the hills fronting the valley are composed of mountain limestone, the higher parts about Shirenewton of the old red sandstone.

On the east side of the Severn, and for some little distance on the western side, the new red sandstone formation is found in nearly horizontal beds. The first disturbance of this takes place behind Portskewett village, where the mountain limestone has been upheaved and the new red formation denuded. A mile farther up the same limestone has been upheaved between Caldicot and Caerwent, and from there to the base of the hills the strata have been much broken, and the